This invention concerns valves adapted to be cleaned by scraping and more particularly to such valves adapted to place a fluid transfer pipe in communication with a selected one of a plurality of other fluid transfer pipes.
A valve according to this invention has utility especially but not exclusively, in the field of transferring liquids such as oil or other petroleum products between supply pipes, storage tanks and draw-off pipes terminating at loading/offloading arms, and other systems for loading road or rail tankers or devices for filling barrels. It may be necessary to connect a supply pipe to a selected one of a plurality of draw-off pipes; a selective fluid distribution valve is used for this purpose.
If the same pipe is used to distribute several liquids in succession a known cleaning process entails shutting of the supply of the first liquid in the pipe on the upstream side and, before opening the supply of the next liquid, also on the upstream side of the pipe, passing a scraper, commonly termed a pig, through the valve from the upstream end to the downstream end and vice versa, the scraper being adapted to scrape clean the inside wall of the pipe so as to remove residues of the first liquid adhering to that wall.
In order to carry out this procedure it is necessary for the pipe and the various valves mounted on it to have the same inside diameter everywhere with no radii of curvature too small to prevent passage of the scraper.
A selective distribution valve adapted to be cleaned by scraping in this way is described in French patent number 2,222,587. This valve or distributor comprises a right-angle elbow section connected at one end to a fixed pipe section through a pivoting articulation or rotary coupling, and at its other end to a junction valve comprising a sliding bushing adapted to be threaded over the end of a selected one of a plurality of draw-off sections distributed angularly in a plane transverse to the fixed pipe section.